Vehicles for ceramic pigments (ceramic mediums) are fluids that are used in the preparation of ceramic inks to disperse ceramic pigments, to regulate their viscosity, flowing properties, and binding-cohesive behaviour.
Most traditional ceramic manufactured products, such as wall tiles and floor tiles, are made of a ceramic body that confers form and mechanical properties to the object; the ceramic body generally has some porosity and poor aesthetic qualities.
Said ceramic body, which is defined “green” or, alternatively, “fired”, if previously fired, is then usually coated with ceramic layer, called ceramic glaze; the ceramic glaze is completely sintered by firing, in such a way to gain suitable superficial aesthetic qualities and, in the meantime, to become a fluid-proof barrier; as a matter of fact, after firing, the ceramic glaze has usually zero porosity and is generally resistant to abrasion and to the attack of chemical agents such as acids, bases, dyes.
The aesthetic finishing of the ceramic material can be completed by a decoration phase, that is by the application of sinterable and variously coloured ceramic materials (ceramic pigments) which are applied according to a precise drawing (décor).
The decor can be applied either on the green or fired ceramic body, on which the glaze was previously set, or, in the so called third firing decorations, after the firing on the glaze.
The ceramic vehicle of the invention is suitable for the décor of green or fired ceramic bodies on which the glaze was previously set.
The main printing techniques used in the decoration either of green or fired ceramic substrate are flat screen printing, rotary screen printing and the decoration by silicone roller (the latter comprising the printing through laser engraved roller, or “rotogravure printing”, and the printing through relief engraved roller, or “silicone stamp printing”); the decoration by silicon roller is also called rotogravure.
All these decoration techniques require a series of overlapping printings, one for each of the colours that compose the drawing. Ceramic inks and vehicles are formulated according to the kind of ceramic body to which they will be applied (green ceramic, fired ceramic, sintered glaze, glass, paper . . . ) and according to the application technique (brush, spatula, screen printing, rotogravure printing . . . ).
In the preparation of ceramic inks for the screen printing or rotogravure decorations of green or fired ceramic bodies, vehicles based on mixtures of water and glycols and normally containing additives, such as rheology modifiers, binders and plasticizers, are generally used.
It is important for the final user that the vehicle is stable, provides stable ceramic inks and décors having good definition.
Vehicles based on water and glycols do possess these requisites, but suffer from some drawbacks too.
In particular, some of the most frequently used glycols, ethylene glycol and diethylene glycol, are labelled as harmful substances.
Furthermore, glycols are industrial products deriving from mineral oil and it is well known that the world oil supply is limited and the price of glycols is subject to wide fluctuations that in the latest years are averagely directed to a strong rise.
Therefore, it would be advantageous to reduce the amount of glycols in the ceramic vehicles without adversely affecting the stability of the ceramic inks and their performance.